I wouldn't worry about it. 5W30 is still good down to -20C which is colder than it's ever likely to get in the UK.
Castrol is a good, reputable brand and as long as the oil matches the stated Toyota specs, the difference between a 0W and a 5W viscosity will not be noticable.
I don't think viscosity is the issue here, and it doesn't seem to be the focus of the OP's concern.
If viscosity were the issue, the very slightly higher viscosity would perhaps give very slightly better wear protection, but probably there'd be no detectable difference.
In other words, it wouldn't matter. This is confirmed by the OP's statement that either 5w30 or 0w30 can be used..
As I understand it, the issue is the exhaust aftertreatment system compatability.
The OP has added a litre of 5w30 ACEA A5/B5 to a system that specifies ACEA C2
C2 is a low SAPS (sulphated ash, phosphorus and sulphur) designed to avoid damage to exhaust aftertreatment systems like the diesel particulate filter.
www.lubrizol.com/en/Lubricant-and-Fuel-Additives/E...0
ACEA A5/B5 isn't. It potentially has higher SAPS, has a higher base number, and a lower level of aftertreatment system compatability.
lubrizol.com/Lubricant-and-Fuel-Additives/Engine-O...0 (specs seem incomplete)
I don't know if the OP has added enough ACEA A5/B5 to compromise his aftertreatment system, but given the reported fragility and expense of these things, I wouldn't dismiss his concerns out of hand.
OP, I suggest you contact the technical department of an oil company with your concerns, but if you want to post on a forum, I'd suggest this US-based oil obsessives site.
bobistheoilguy.com/forums/ubbthreads.php/forums/52..._(PCMO)
|